Method for lotioned tissue ply attachment

ABSTRACT

Ply attachment for multiply lotioned tissue products is accomplished by distributing thermoplastic particles between the plies and melting the thermoplastic particles to bond together the fibers of the two plies.

This is a divisional of Ser. No. 07/124,635 filed Nov. 24, 1987, nowU.S. Pat. No. 4,806,418, which is a continuation of Ser. No. 06/895,074filed Aug. 11, 1986, now abandoned.

In the manufacture of facial tissue, two-ply products are typically heldtogether by crimping the edges of the two plies. However, recently someproducts have been developed which contain lotions or other ingredientswhich act to inhibit ply attachment by crimping. For example, U.S. Pat.No. 4,481,243 to Allen describes a lotioned tissue product which isdesigned to sooth the user's skin. Because the lotion preventssuccessful edge crimping, the lotion is applied only to areas of thetissue which are not to be crimped, namely the center of the tissue.This of course leaves areas of the tissue which are untreated and arepotentially irritating to the user.

Therefore there is a need for a method of ply attachment which is notsensitive to the ingredients contained within treated tissues.

SUMMARY OF THE INVENTION

In general, the invention resides in a method for attaching together twoplies of tissue, such as facial and bath tissue and the like,comprising: (a) distributing thermoplastic particles over one surface ofa first tissue ply; (b) bringing a second tissue ply into contactingrelationship with the thermoplastic particle-containing surface of thefirst tissue ply; (c) melting or softening the thermoplastic particles;and (d) solidifying the melted or softened thermoplastic particleswhereby the first and second tissue plies become bonded together.Although this method can be used to attach together two or more plies ofany tissue, it is particularly advantageous for attaching togethertissue plies wherein one or both of the plies contain ingredients suchas emollients, lotions, oils, and the like, the presence of whichprevents attachment by crimping. For purposes herein, these variousingredients are lumped together into the single term "lotion."

The thermoplastic particles can be distributed over the surface in anydesired pattern, although a light overall dusting of one ply ispreferred for convenience. A suitable means for distributing theparticles is described in U.S. Pat. No. 4,561,380 to Mulder et al.,which is incorporated herein by reference. However, it is within thescope of this invention that the thermoplastic particles be distributedon or within the ply or plies in any suitable manner, such as byincorporating the particles into the furnish and forming the plies withthe thermoplastic particles contained therein. Alternatively thethermoplastic particles can be applied to the surface of one or bothplies at distinct spaced-apart spots or in a line pattern.

In order for ply attachment (bonding) to occur, the second ply must bebrought into a contacting relationship with the thermoplasticparticle-containing surface of the first ply. The necessary contact,heating, and cooling is most easily accomplished in a heated nip, inwhich the thermoplastic particles are melted or otherwise sufficientlysoftened and cooled to bond the plies together. Because the moltenthermoplastic envelops the individual fibers of both plies, uponhardening the two plies become bonded together. As such this method iseffective regardless of the presence of fiber coatings which wouldotherwise prevent intra-fiber chemical bonding. Although a heated nip isthe most convenient method of achieving ply attachment in accordancewith this invention, other means of melting the thermoplastic polymerare also within the scope of this invention, such as the use ofultrasonic bonding or radio frequency sealing.

The particular thermoplastic polymers preferred for use in the method ofthis invention are polyethylene and polypropylene because of theiravailability and low cost. However, any thermoplastic polymer issuitable from a purely technical standpoint. The particle size of thethermoplastic particle is of some importance in that the particles mustbe small enough to avoid adverse effects on the perceived softness ofthe tissue product. In general, the thermoplastic particles should besmall enough to pass through a 20 mesh screen. Particles larger than 20mesh can be detected in the tissue. In addition, when larger particlesare present, the melted thermoplastic may penetrate the tissue web andcause blocking when the web is wound onto a roll. (For purposes herein,mesh size is as defined in ASTM D-1921.) A suitable form ofthermoplastic particle is commercially available under the name"Microthene" from U.S.I. Corporation. This product is available indifferent grades of a very fine polyolefin powder having different meshsizes.

For facial tissue, the particle distribution over the surface of thefirst ply should be less than about 0.0025 grams per square inch inorder to avoid an overly stiff product. The particle density will dependgreatly on the particle size and the desired bond strength between theplies. A particle density of about 0.0006 grams per square inch or lesis preferred for facial and bath tissue, but in any particular case theparticle density will depend upon the nature of the product and itsintended use. Heavier basis weight products, such as wipes and papertowels, may need stronger ply attachment and can use higher particledensities because any resulting increase in stiffness is less noticeableor critical.

EXAMPLES

In order to further illustrate the method of this invention, acommerciallyavailable lotion-treated ply of facial tissue was dustedwith a low densitypolyethylene powder. The lotion contained mineral oil,cetearyl alcohol, and steareth-2 and was present in the ply at a levelof about 12 percent by weight. The polyethylene powder was MicrotheneMN714, which is a 50 mesh material. The powder was evenly distributedover the surface of the lotion-treated tissue using a small shaker tray.A second lotion-treated ply was laid on top of the first and brieflycompressed with a heated laboratory iron (280° F. surface temperature).The iron caused the polyethylene powder to melt and bind the two pliestogether. This procedure was repeated for the following powder densities(grams per square inch): 0.000625, 0.00125, 0.0025, 0.00625, 0.0125 and0.01875. In all cases the ply bonding was strong enough to tear theplies when separated, even at the lowest level of powder addition,illustrating the effectiveness of this method.

It must also be pointed out that the method of this invention can beutilized to produce multiply tissue products wherein the lotion isappliedsimultaneously with the thermoplastic particles. For example,encapsulated lotions are available in microbead form which can beapplied to the tissuewith the thermoplastic bonding particles. In thiscase, the lotion is released when the two plies are bonded together.

It will be appreciated that the foregoing examples, shown for purposesof illustration, are not to be construed as limiting the scope of thisinvention.

I claim:
 1. A method for attaching together two plies of tissue whereinat least one of said tissue plies contains lotion, said methodcomprising:(a) distributing less than about 0.0025 grams ofthermoplastic particles per square inch over one surface of a firsttissue ply; (b) bringing a second tissue ply into contactingrelationship with the thermoplastic particle-containing surface of thefirst tissue ply; (c) melting or softening the thermoplastic particles;and (d) solidifying the melted or softened thermoplastic particles,whereby the first and second tissue plies become bonded together wherelotion is present.
 2. The method of claim 1 wherein the first tissue plycontains lotion and the second tissue ply does not contain lotion. 3.The method of claim 1 wherein the second tissue ply contains lotion andthe first tissue ply does not contain lotion.
 4. The method of claim 7wherein the first and second tissue plies both contain lotion.
 5. Themethod of claim 1 wherein the solidified thermoplastic particles aredistributed evenly over the surface of the first ply.
 6. The method ofclaim 5 wherein the particle distribution over the surface of the firstply is less than about 0.0006 grams per square inch.
 7. The method ofclaim 6 wherein the thermoplastic particles are polyethylene.